removing multiple identical references from bib-file

[Wolfgang Engelmann]

I am using jabref for my references and would like to remove multiple 
identical items (e.g. same author(s), title, year). With Jabref this is 
cumbersome (at least I haven't found a better method yet) by clicking at 
"keep upper/lower" ...
I wouldn'd mind to switch to another program for this purpose or use a 
script to do that. Can somebody give me a hint?
Wolfgang